Rectifier Upgrade

[phx5kegsman]

I have a 1978 Johnson 115hp V4 crossflow that this fine group has helped me with several times. I have been having issues with my Tachometer showing 10k rpm's more than the engine is going (ex. tach reads 72k at WOT). Also, my voltmeter gauge is pegged at around 16V once the motor is warmed up. The rectifier failed the Ohms test that's outlined in the manual. While shopping online I came across an aftermarket replacement that is the rectifier, but has a voltage regulator added to it. It's made by CDI, but sold as Sierra brand. Maybe they've merged or something. Anyway, has anyone seen, or used, this rectifier + regulator?? Is it worth getting?

 

[Crosbyman]

i doubt adding a regulator function would cause concerns. Such parts and plain jane rectifiers are dirt cheap on Amazon and could be mounted as a replacement to expensive OEM.. up to you

 

[phx5kegsman]

is there any benefit from the added regulator? The original is only a rectifier.

 

[Crosbyman]

speaks for itself doesn't it ? also protects accessories from power spikes, over voltages etc..

 

[saltchuckmatt]

I'm confused, tach shows 10k....but you run at 7200 RPM's at wot? I hope I'm wrong...please explain.

Also, if your rectifier is cooked, you won't see 16 volts. You will see whatever the battery voltage is.

 

[Mc Tool]

Could be 16vac? , but in any event to see 16v the reg must be duff or have earthing issues . If you could make a suitable reg/rect fit I would do that .

 

[flyingscott]

Sounds like your rectifier is working correctly. Have you checked your tach? On the right setting?

 

[Berdink]

With your motor off. Check the voltage at your battery terminals/posts with a multimeter. It should be around 12.8v.
Then, with the motor running, check the voltage at the battery again with the multimeter.
Is it reading 16v, or closer to 13v?

 

[Chris1956]

Gee, if you get an aftermarket voltage rectifier, it needs to be sealed against sparks. Sparks under the OB cowling are quite dangerous.

 

[Mc Tool]

Gee, if you get an aftermarket voltage rectifier, it needs to be sealed against sparks. Sparks under the OB cowling are quite dangerous.

Yeah , you wouldnt want to put high voltage coils or spark plugs under there.

 

[jimmbo]

An Unregulated Charging System hitting 16 volts in pretty much normal at high Rpms. Those charging systems don't put out much Current, and simply use the Battery(Wet Cell ONLY), as a sacrificial Reservoir, boiling when the Voltage is high. After the drain on the battery, from cranking, and use of the Power Trim, and other Accessories in the boat, the battery is rarely returned to a fully charged state. If you are trying to use an AGM Battery, then the System, regardless of how low Amperage it is, will need a Regulator.

 

[saltchuckmatt]

And no explanation/confirmation from the op

 

[phx5kegsman]

Sorry for the lag time. I will check battery voltage today, while running in tank. I will also check tach settings. The tach, sometimes, is sitting on 10k before I start the motor, with the key on. It only does this after motor runs for a while. On initial startup after sitting for a while. After battery switch has been off and then back on, the tach is at 0.
It's not, actually running at 72k at WOT (it would blow up, wouldn't it?), but that is what the tach reads.
Also, I'm using a wet cell deep cycle battery

 

[Chris1956]

Tachs do not last forever. I would rotate the tach settings to get any corrosion off of them.

Tachs run off the raw AC stator voltage. You can therefore connect them as such. VRs usually have a grey tach feed, which is just the raw AC voltage from the stator. Disconnect the rectifier and connect the tach to the yellow stator wire and see if it works better. If not, the tach is likely bad.